The Arthropod Head

Richter, Stefan; Stein, Martin; Frase, Thomas; Szucsich, Nikolaus U.

doi:10.1007/978-3-642-36160-9_10

Cited by 19 publications

(14 citation statements)

References 107 publications

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“…As expressed in previous publications, we support the idea put forward by Scholtz and Edgecombe () that the frontal filaments of crustaceans are homologous to the primary antenna of Onychophora, but up until now were uncertain about the origin of the labrum (see Frase and Richter, ; Richter et al, ). Recently, Ortega‐Hernández and Budd () revealed interesting paleontological data homologizing the crustacean frontal filaments with the “frontal processes,”or first pair of lip papillae in Onychophora, and the onychophoran primary antenna with the (deuteropod) hypostome/labrum complex (see also Scholtz and Edgecombe, ; Eriksson et al, ; Steinmetz et al, ; Strausfeld, ).…”

Section: Discussionsupporting

confidence: 88%

Nervous system development in the fairy shrimpBranchinellasp. (Crustacea: Branchiopoda: Anostraca): Insights into the development and evolution of the branchiopod brain and its sensory organs

Frase

Richter

2016

Journal of Morphology

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Using immunohistochemical labeling against acetylated a-tubulin and serotonin in combination with confocal laser scanning microscopy and 3D-reconstruction, we investigated the temporary freshwater pond inhabitant Branchinella sp. (Crustacea: Branchiopoda: Anostraca) for the first time to provide detailed data on the development of the anostracan nervous system. Protocerebral sense organs such as the nauplius eye and frontal filament organs are present as early as the hatching stage L0. In the postnaupliar region, two terminal pioneer neurons grow from posterior to anterior to connect the mandibular neuromeres. The first protocerebral neuropil to emerge is not part of the central complex but represents the median neuropil, and begins to develop from L0+ onwards. In stage L3, the first evidence of developing compound eyes is visible. This is followed by the formation of the visual neuropils and the neuropils of the central complex in the protocerebrum. From the deutocerebral lobes, the projecting neuron tract proceeds to both sides of the lateral protocerebrum, forming a chiasma just behind the central body. In the postnaupliar region, the peripheral nervous system, commissures and connectives develop along an anterior-posterior gradient after the fasciculation of the terminal pioneer neurons with the mandibular neuromere. The peripheral nervous system in the thoracic segments consists of two longitudinal neurite bundles on each side which connect the intersegmental nerves, together with the ventral nervous system forming an orthogon-like network. Here, we discuss, among other things, the evidence of a fourth nauplius eye nerve and decussating projecting neuron tract found in Branchinella sp., and provide arguments to support our view that the crustacean frontal filament (organ) and onychophoran primary antenna are homologous. J. Morphol. 277:1423-1446, 2016. © 2016 Wiley Periodicals, Inc.

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Section: Discussionsupporting

confidence: 88%

Nervous system development in the fairy shrimpBranchinellasp. (Crustacea: Branchiopoda: Anostraca): Insights into the development and evolution of the branchiopod brain and its sensory organs

Frase

Richter

2016

Journal of Morphology

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“…Therefore, it has been suggested that conclusions concerning labrum homology based on the expression of single genes should be considered carefully (Janssen 2017). An alternative hypothesis suggests that the labrum does not have an appendicular origin, but is instead homologous to the anterior-most pair of lip papillae of onychophorans, while the onychophoran antennae, in turn, might be homologous to the frontal filaments of some crustaceans Richter 2013, 2016;Richter et al 2013). The latter assumption is based on the fact that the frontal filaments in the anostracan crustaceans Branchinella sp.…”

Section: Evolution Of the Panarthropod Brain And Segmental Identity Omentioning

confidence: 99%

The nervous and visual systems of onychophorans and tardigrades: learning about arthropod evolution from their closest relatives

et al. 2017

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Understanding the origin and evolution of arthropods requires examining their closest outgroups, the tardigrades (water bears) and onychophorans (velvet worms). Despite the rise of molecular techniques, the phylogenetic positions of tardigrades and onychophorans in the panarthropod tree (onychophorans + tardigrades + arthropods) remain unresolved. Hence, these methods alone are currently insufficient for clarifying the panarthropod topology. Therefore, the evolution of different morphological traits, such as one of the most intriguing features of panarthropods-their nervous system-becomes essential for shedding light on the origin and evolution of arthropods and their relatives within the Panarthropoda. In this review, we summarise current knowledge of the evolution of panarthropod nervous and visual systems. In particular, we focus on the evolution of segmental ganglia, the segmental identity of brain regions, and the visual system from morphological and developmental perspectives. In so doing, we address some of the many controversies surrounding these topics, such as the homology of the onychophoran eyes to those of arthropods as well as the segmentation of the tardigrade brain. Finally, we attempt to reconstruct the most likely state of these systems in the last common ancestors of arthropods and panarthropods based on what is currently known about tardigrades and onychophorans.

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“…Another topic addressed here is the morphology and evolution of the mandibulate head (traditionally termed “cephalon” in Crustacea) and its segments (see e.g., Lauterbach, ; Budd, ; Waloszek et al, ; Scholtz and Edgecombe, ; Giribet and Edgecombe, ; Richter et al, ). Although the maxillar segment (Mx2) forms part of the cephalon in all recent mandibulates, the anatomy of maxillar appendages is morphologically disparate.…”

Section: Introductionmentioning

confidence: 99%

The ventral nerve cord in Cephalocarida (Crustacea): New insights into the ground pattern of Tetraconata

Stegner

Brenneis

Richter

2013

Journal of Morphology

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Cephalocarida are Crustacea with many anatomical features that have been interpreted as plesiomorphic with respect to crustaceans or Tetraconata. While the ventral nerve cord (VNC) has been investigated in many other arthropods to address phylogenetic and evolutionary questions, the few studies that exist on the cephalocarid VNC date back 20 years, and data pertaining to neuroactive substances in particular are too sparse for comparison. We reinvestigated the VNC of adult Hutchinsoniella macracantha in detail, combining immunolabeling (tubulin, serotonin, RFamide, histamine) and nuclear stains with confocal laser microscopy, complemented by 3D-reconstructions based on serial semithin sections. The subesophageal ganglion in Cephalocarida comprises three segmental neuromeres (Md, Mx1, Mx2), while a separate ganglion occurs in all thoracic segments and abdominal segments 1-8. Abdominal segments 9 and 10 and the telson are free of ganglia. The maxillar neuromere and the thoracic ganglia correspond closely in their limb innervation pattern, their pattern of mostly four segmental commissures and in displaying up to six individually identified serotonin-like immunoreactive neurons per body side, which exceeds the number found in most other tetraconates. Only two commissures and two serotonin-like immunoreactive neurons per side are present in abdominal ganglia. The stomatogastric nervous system in H. macracantha corresponds to that in other crustaceans and includes, among other structures, a pair of lateral neurite bundles. These innervate the gut as well as various trunk muscles and are, uniquely, linked to the unpaired median neurite bundle. We propose that most features of the cephalocarid ventral nerve cord (VNC) are plesiomorphic with respect to the tetraconate ground pattern. Further, we suggest that this ground pattern includes more serotonin-like neurons than hitherto assumed, and argue that a sister-group relationship between Cephalocarida and Remipedia, as favored by recent molecular analyses, finds no neuroanatomical support.

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The Arthropod Head

Cited by 19 publications

References 107 publications

Nervous system development in the fairy shrimpBranchinellasp. (Crustacea: Branchiopoda: Anostraca): Insights into the development and evolution of the branchiopod brain and its sensory organs

Nervous system development in the fairy shrimpBranchinellasp. (Crustacea: Branchiopoda: Anostraca): Insights into the development and evolution of the branchiopod brain and its sensory organs

The nervous and visual systems of onychophorans and tardigrades: learning about arthropod evolution from their closest relatives

The ventral nerve cord in Cephalocarida (Crustacea): New insights into the ground pattern of Tetraconata

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